A Spatial Referencing Policy
for the Province of Nova Scotia
A Spatial Referencing Policy for the Province of Nova Scotia
Policy Document
January, 2006
By GeoNOVA Reference Coordinate System Policy Node
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A Spatial Referencing Policy
for the Province of Nova Scotia
Table of Contents
1.0
Purpose
1.1
Why a reference coordinate system
1.2
What is a reference coordinate system
2.0
Nova Scotia’s Policies Related to Spatial Referencing
2.1
Introduction
2.2
Policies
2.2.1 Operational Policies
Policy 1.0
Administration
Policy 2.0
Operational Approach
Policy 3.0
Consultation: Engaging Stakeholders
Policy 4.0
Communications: Opening Dialogue
Policy 5.0
Standards: Federal - Provincial
2.2.2 Technical Policies (Geodetic Reference Standards)
Policy 6.0
Geodetic Reference System
Policy 7.0
Monitoring Change
Policy 8.0
Coordinate Transformation Services
Policy 9.0
Nova Scotia Coordinate Control System (NSCCS) Network
Policy 10.0 Vertical Reference System
Policy 11.0 Nova Scotia High Precision Network (NSHPN)
Policy 12.0 Error Ellipse Information
Policy 13.0 Metadata
2.2.3 Technical Policies (Map Projections)
Policy 14.0 Small Scale Map Projections
Policy 15.0 Large Scale Map Projections
Policy 16.0 Grid Shift Files
Appendix A A Historical Perspective on the Nova Scotia Coordinate Reference System
Appendix B Policy Matrix
Appendix C Terminology
Appendix D Reference Material
Figures:
1.0
Hierarchy of Canadian Spatial Reference System from the NSCRS Perspective
A.1
History of the Reference System for Nova Scotia
A.2
MTM Zones for Nova Scotia
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A Spatial Referencing Policy
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1.0
Purpose
The positioning user community in Nova Scotia is very diverse. They come from different
sectors (industry, government, and general public) with different applications and accuracy
requirements. The growth in the use of satellite positioning systems, GIS, and the integration
and exchange of geospatial data have made it necessary to review and formalize a new spatial
referencing policy for the Province.
The specific purpose herein is to document the policies regarding spatial referencing in Nova
Scotia and provide direction as to the operational requirements to support and facilitate these
policies. Through the documentation of formal policies the Province is providing an enabling
infrastructure upon which all subsequent geo-spatial, primary and or thematic, databases are
built/supported.
In addition to documenting the specific policies which help to govern the Nova Scotia
Coordinate Reference System the reader is also provided with an understanding of the
terminology and practices that must be undertaken to support this infrastructure. As well, as can
be found in Appendix A, a historical overview is also provided so as to help the reader
understand the evolution of this corporate coordinate reference system.
1.1
Why a reference coordinate system
Describing an individual’s position/location, or that of a topographic feature or object, on or near
the surface of the earth with a level of certainty and in a simple numerical way is one of the basic
requirements for databases and applications with a geospatial context. Today, primarily due to
Global Positioning System (GPS) technology, one sees positioning at work in more applications
than ever. Agencies mapping topographic features; engineers and surveyors designing and laying
out new structures; vehicles with navigation capabilities; cell phones with location capability;
environmental planning/management tasks; boundary demarcation; etc. are but some examples
where positioning is applied.
The most convenient way to describe the position of a point or feature on or near the surface of
the earth is with a “well-defined” coordinate system – a coordinate system with a defined origin,
orientation of the axes, and scale. This will enable a position described in that coordinate system
to be stated uniquely as an unambiguous set of numbers – the basics of this concept is seen in the
two-dimensional rectangular coordinate system learned in grade school to plot coordinates on a
piece of paper. Here though, one is dealing with the “real world” which is three-dimensional, or
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A Spatial Referencing Policy
for the Province of Nova Scotia
four dimensional when time has to be considered and it must be related to the earth rather than a
piece of paper. Such a coordinate system becomes a reference coordinate system and forms part
of a spatial reference system or reference system.
The task of determining a position is called positioning or some may use the term spatial
referencing. Spatial referencing and, the use and exchange of geospatial data can be greatly
facilitated if a common reference system is used. Within the Province there are many geospatial
applications where positioning and the use of a common reference coordinate system is very
important. The provision of a reference coordinate system at the provincial level and access to it
in fact, has been a mission/mandate of the province since at least the mid 1960’s. It is one of the
fundamental infrastructure components required in the management of the Province’s geographic
information, as well as serving as a reference system to the positioning community operating at
large within Nova Scotia.
1.2
What is a reference coordinate system
A reference coordinate system is essentially one in which the origin, the orientation of the axis
and the scale have been defined. The category of coordinate system of interest here is the
terrestrial one (as opposed to a celestial one or orbital one) as they are defined with respect to the
earth and are designed to describe the position of points on or near the surface of the earth. They
are fixed to earth, spin with the earth and revolve with the earth.
In today’s terminology a distinction is made (by some) between the conceptual definition of a
coordinate system and, the practical realization of that coordinate system through observations.
The term reference system is used to refer to the complete conceptual definition of how a
coordinate system is formed. It defines the origin, orientation of the system axes and also
includes the underlying fundamental mathematical and physical models used in the treatment of
observed quantities. A practical realization of the reference system on the other hand is known as
a reference frame. It materializes (“realizes”) the coordinate system into something tangible and
accessible by positioning users. It consists of a set of identifiable, accessible physical points (ie.
frame points) with precisely determined coordinates in a specific coordinate system at a specific
epoch.
The reference frame serves as the physical set of points with associated coordinates from which
the position of other points and features may be determined or to which other points and features
are ultimately spatially referenced. Thus the reference frame provides the geometrically
consistent physical structure that is the foundation for positioning tasks and to which the spatial
component of real world features can be referenced.
Since very specialized procedures are used to determine the position of the frame points, there
usually is only a relatively sparse set of such points established within the system. These points
are used to connect other surveys and establish geodetic control networks, thereby extending the
reference frame and making the reference system more widely applicable to the positioning user.
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Today with the use of GPS technology it is also possible for users to access the reference system
without directly occupying the monumented network points - the GPS satellites are in effect a
reference frame. However, GPS must be used appropriately if the derived positions are to be
referenced to the reference system used by the province.
In Canada the task of providing the spatial reference system and making it accessible is carried
out by the federal and provincial geodetic agencies in a cooperative and structured fashion (see
Figure 1.0) At the provincial level, the Nova Scotia Coordinate Reference System (NSCRS) is
the all encompassing term used to describe the collection of reference systems and their
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Figure 1.0 Hierarchy of Canadian Spatial Reference System from the NSCRS Perspective
associated realizations (past, present and future), related data, geodetic software, other geodetic
components and associated products and services, which together constitute the Provincial
spatial reference standard and its supporting infrastructure. This establishes and maintains the
provincial reference frame and provides for a quantitative description of positions in Nova Scotia
: the reference frame of the NSCRS is integrated with, and is an extension of, the national
reference frame belonging to the Canadian Spatial Reference System (CSRS).
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The NSCRS is an enabling geomatics infrastructure providing spatial context to the Province’s
primary and thematic databases. A well documented, and maintained, reference coordinate
system provides credibility to geographic data holdings and allows people to associate their data
within the real world. A reference coordinate system when properly applied, facilitates the
production of quality geographic products to be generated for the end user.
2.0
Nova Scotia’s Policies Related to Spatial Referencing
Given the diversity in geomatics activities within the Province of Nova Scotia and the growth in
technologies deployed to support such an industry, these policies are provided for the benefit of
all geomatics practitioners in, or who do business within, Nova Scotia.
2.1
Introduction 1
In fiscal 2003/04 Service Nova Scotia and Municipal Relations (SNSMR) initiated an extensive
consultation process with a large cross section of users of the NSCRS including government
departments and agencies, businesses and general users. The purpose of this consultation was to
review the needs of the positioning user community and to determine what steps needed to be
taken to formally adopt a series of policies and management strategies so as to enhance the
delivery of the NSCRS program.
SNSMR’s business plan continues to strengthen government’s commitment to seeing a
documented and approved set of policies related to spatial referencing. SNSMR’s Business Plan
notes that it is responsible for ensuring results in the following areas [excerpt from SNSMR 2004/05
Business Plan]:
!
Collaboration with internal and external partners to evaluate and improve the quality and
effectiveness of government services.
!
Policy development for the Department in the areas of data privacy, security and access
and integrity of data holdings.
!
Customer and stakeholder satisfaction with SNSMR services.
!
Effective and positive relationships with other levels of government, provincial
departments and agencies and the private sector.
It is based upon these commitments that the spatial referencing policies contained within this
document are presented.
As identified in the consultation process, the reference coordinate system for Nova Scotia must
be or do all of the following:
1
In preparing the content for this policy document it has become evident that terminology surrounding Nova Scotia
geodetic infrastructure has evolved. The terminology employed here is intended to be the foundation terminology
upon which Nova Scotia will continue to promote, support and build from this point forward. A Glossary of Terms
and Terminology is provided at the end of this document so as to assist with the changes.
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!
!
!
!
!
simple to use;
accurate, reliable, and consistent for surveying;
stable over the long term;
achievable with a minimum of hardship for users; and
provide for an accommodation of future eventualities.
But as well the management of the system, i.e. the policies and management strategies must also
consider these criteria.
The Province must ensure that the integrity of the reference system is addressed both in the
immediate and the longer term. It must also ensure that the reference frame itself is maintained to
a high enough quality so that it is capable of supporting a wide range of applications, with
accuracy requirements ranging from the low to the high end of the spectrum.
2.2
Policies
The policies related to spatial referencing are categorized to include Operational Policies and
Technical Policies (for reference frame and map projections). These policies come as a direct
result of the in depth consultation efforts in fiscal 2003/04. During that consultation there were
areas where stakeholders thought policies were necessary or beneficial. In reviewing the
material, it has been determined that some issues are not specifically of a policy nature but are a
business process or strategic issue and thus have not been incorporated in this document. Please
refer to Appendix B which correlates the findings from the Final Report for the Study of the
Official Adoption of the NSCRS [September 2003] and the policies presented here.
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2.2.1
Operational Policies:
Policy 1.0
Administration
The NSCRS will continue to be administered by Service Nova Scotia and Municipal
Relations, through Registry and Information Management Services, specifically the
Geographic Information Services Section. The Nova Scotia Geomatics Centre will be the
agent responsible for this administration.
Policy 2.0
Operational Approach
SNSMR, through the Geographic Information Services and specifically the Nova Scotia
Geomatics Centre will develop and deliver an Operational Strategy related to the NSCRS
. Subject matter within the strategy will include, but will not be limited to:
communications; training; specifications; and services.
Policy 3.0
Consultation: Engaging Stakeholders
The Province will establish a consultation process to engage stakeholders involved in the
use of spatial referencing. This process will be initiated when:
•
NSCRS standards need to be addressed, e.g. when a new realization is
being considered.
•
Regulations governing spatial referencing are altered.
•
Policies governing spatial referencing require updating.
Policy 4.0
Communications: Opening Dialogue
The Province will ensure operations related to the delivery of the NSCRS are
communicated to the geomatics community of Nova Scotia. They will further ensure that
positioning practitioners have a means upon which they can provide input into the
delivery of the NSCRS. This may include delivery of an annual communications plan and
the specific actions against such a plan e.g. information seminars, industry trends, etc.
Policy 5.0
Standards: Federal - Provincial
The Province will continue to operate within the context of the CSRS and where
applicable will adopt national standards and specifications for the NSCRS.
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2.2.2
Technical Policies (Geodetic Reference Standard):
Policy 6.0
Geodetic Reference System
The Province will implement NAD83(CSRS) as the spatial reference frame standard
within the NSCRS. Specific NAD83(CSRS) versioning will be communicated as part of
the deliverables from Policy 2.0
Policy 7.0
Monitoring Change
The Province will monitor all changes to the reference frame that might impact the
NSCRS and will inform the positioning user community when changes are detected.
Policy 8.0
Coordinate Transformation Services
The Province will deliver coordinate transformation services so as to ease the conversion
burden experienced when transforming data from one projection and reference frame to
another. This service may include, but is not limited to:
•
training workshops
software tools (e.g. web enabled solutions)
•
•
advisory services
•
and will target a variety of data dissemination methods
Policy 9.0
Nova Scotia Coordinate Control System (NSCCS) Network
The Province will provide the NAD83(CSRS) horizontal coordinates and absolute
accuracy estimate (95% confidence level) for the Nova Scotia Coordinate Control
System(NSCCS) network of control points. The coordinates and absolute accuracy
estimate will be derived from an adjustment in which the acceptable, existing
conventional observation data from this network is integrated with the Nova Scotia High
Precision Network (NSHPN). Control points within the NSCCS network with insufficient
and/or unacceptable observations will be removed from the adjustment and thus will not
obtain NAD83(CSRS) coordinates. Situations leading to this are:
•
after removal of unacceptable observations, there is insufficient
observations remaining to properly define the point
•
insufficient observations to define the point to begin with
•
unresolved adjustment / observation issues in an area of the network, leads
to removal of all control points within that portion of the network.
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Policy 10.0
Vertical Reference System
The Canadian Geodetic Vertical Datum of 1928 (CGVD28) will continue as the
Province’s vertical reference standard for the near term. The Province is committed to
monitoring developments with the vertical reference system, in association with the
Geodetic Survey Division of Natural Resources Canada.
Policy 11.0
Nova Scotia High Precision Network (NSHPN)
The NSHPN will be the set of points at the provincial level, defining the NAD83(CSRS)
reference frame for the NSCRS. The physical maintenance of this network remain the
responsibility of the Department of Service Nova Scotia and Municipal Relations
Policy 12.0
Error Ellipse Information
The Province will publish the error ellipse information for any NAD83(CSRS) coordinate
for control points within the NSCRS.
Policy 13.0
Metadata
The Province will publish collection and product level metadata pertinent to the
Province’s spatial reference system. This metadata will be documented against the
provincial metadata standard and will be made available within the Nova Scotia Metadata
repository.
2.2.3
Technical Policies (Map Projections):
Policy 14.0
Small Scale Map Projections
The Province adopts the Universal Transverse Mercator (UTM) Map Projection, and
NAD83(CSRS), as the standard map projection and reference frame, to be used in the
Province of Nova Scotia for all Primary Database Mapping at scales of 1:10,000 and
smaller (scales smaller than 1:10,000 would include scales at 1:25,000; 1:50,000 ;
1:500,000; etc.). Thematic data custodians will apply the same standard where
appropriate.
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Policy 15.0
Large Scale Map Projections
The Province adopts the Nova Scotia 3 degree Modified Transverse Mercator Map
Projection (NSMTM), and NAD83(CSRS), as the standard map projection and reference
frame, to be used in the Province of Nova Scotia for all Primary Database Mapping at
scales larger than 1:10,000. (scales larger than 1:10,000 would include scales at 1:5,000;
1:2,000; 1:1,000; etc.) Thematic data custodians will apply the same standard where
appropriate.
Policy 16.0
Grid Shift Files
The Province will distribute the grid shift file for transformations between ATS77 and
NAD83 (CSRS).
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APPENDIX A
A Historical Perspective on the Nova Scotia Coordinate Reference
System
The history of establishing the national reference coordinate system which was used in Nova
Scotia can be dated back into the 1900's. Figure A.1 provides a very high level snap shot of the
developments of the reference system for Nova Scotia.
The reference coordinate system for the Province of Nova Scotia was initiated in March 1968
under the Atlantic Provinces Surveying and Mapping Program (APSAMP). During the first five
years of operation the Province placed a total of 8000 control points throughout the developed
areas of the Province. By 1981 some 23000 control points were established in the Province thus
completing the control network of its day. This network became known as the Nova Scotia
Coordinate Control System (NSCCS).
In 1982, following the establishment of the 23000 control points, a maintenance program for the
system was established. The maintenance program was managed jointly for all three Maritime
Provinces through the Land Registration and Information Service (LRIS) Program. Between
1993 and 1998 the Province established the Nova Scotia High Precision Network (NSHPN) and
which today contains 153 points, observed by GPS and based upon NAD83(CSRS).
In 1994 the LRIS Program ended, leaving responsibility for the control system in the hands of
the individual Provinces. Today(2005) the system in Nova Scotia is managed by Nova Scotia
Department of Service Nova Scotia and Municipal Relations, under the administration of
Geographic Information Services and more specifically the Nova Scotia Geomatics Centre
(NSGC).
Geographic Information Services has been mandated to develop, maintain and distribute
corporate geographic information assets. The NSCRS is one of those corporate assets but more
importantly it is the “foundation” upon which all other corporate databases are built. Geographic
Information Services thus manages and delivers the NSCRS in consultation with the positioning
user community of Nova Scotia.
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A B C D E
F
G
A
National First Order Surveys / Local Coordinate Systems
Project Specific Activities
B
Provincial Monumentation
C, D
Major NAD 27 Regional Adjustment
E
ATS77 Redefinition / Readjustments
F
Initiation of NAD83 (NSHPN Starts Installation)
G
NSHPN Complete Installation
H
NSHPN 1.0 Published NAD83 CSRS
2000+
1998
1993
1979
1972
1968
1960’s
1900’s
A Spatial Referencing Policy
for the Province of Nova Scotia
H
Figure A.1
History of the Reference System for Nova Scotia
In recent history the Province has looked to formalize its reference system and its spatial referencing
activities. The document A Coordinate Referencing Policy for the Province of Nova Scotia was
released in November 1995 and contains recommendations and draft policy statements regarding
coordinate referencing for the Province of Nova Scotia. It was in essence the initial formulation of
the administrative strategy to deal with two major developments in positioning that emerged in the
early 1990's. They were, (1) the increasing use of GPS technology and (2) the upgrade being made
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by geodetic agencies related to their reference frame standard and subsequent compatibility with
GPS use. Many of the recommendations and policy statements contained in the 1995 document
were based on recommendations from an earlier report, The Report of the Task Force on Control
Surveys in the Maritime Provinces [1993].
In the 1995 work, the term Nova Scotia Coordinate Reference System (NSCRS) was introduced as
the all-encompassing term used to describe the coordinate reference system proposed for the
province. The NSCRS concept is very broad in scope and encompasses a number of spatial
reference components. The 1995 document outlines the function of the NSCRS as being: to serve
as the reference or foundation for all provincial positioning uses and to be the reference upon which
the spatial component of provincial geospatial databases are based. One of the recommendations
was to upgrade the spatial reference frame used for the NSCRS to NAD83 and more specifically the
NAD83(CSRS) realization. A completion date was not set, as there was preparation work to be
done and other factors to take into account before setting such a date, one being user
acceptance/readiness.
Nova Scotia has been working with the federal government along with other provinces and now has
in place a network of control points with NAD83(CSRS) coordinates. There also is a grid shift file
(NS778301.gsb) for use in transforming between ATS77 and NAD83(CSRS). A GPS correction
service known as the Canada-wide Differential Global Positioning System (CDGPS) Service is now
in place. The CDGPS was developed by the ten provinces, the Government of Nunavut, and the
Government of Canada. It provides GPS corrections based on NAD83(CSRS). Also in the Atlantic
region is the Canadian Coast Guard differential correction service. Thus there is broad access to
NAD83(CSRS) within the province.
Since 1979, the de facto reference frame standard, for the province, has been the Average Terrestrial
System of 1977 (ATS77). It superseded the NAD27 frame. The provincial map projection utilized
with it and in which most provincial corporate geospatial data is maintained is the Nova Scotia
MTM projection. Two zones, 4 and 5, with slightly extended zone boundaries beyond the 3E band
at the eastern and western extremities of the province are required for provincial coverage (see
Figure A.2). While ATS77 was a significant improvement over NAD27, it is not the reference
frame currently used for the Canadian Spatial Reference System (CSRS) nor is ATS77 compatible
with GPS where WGS84 is used. This makes work more complex when exchanging geospatial data
with other jurisdictions or integrating GPS position data with ATS77 based position data.
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Figure A.2 MTM Zones for Nova Scotia
These various activities (back room processes, improvements to the system, extensive user
consultations, etc.) supported the move to formalize the NSCRS. Such action will provide a
reference system compatible with GPS and ease the burden when exchanging geospatial data with
other jurisdictions. The positioning user community supports the move forward in the application
of this reference system and much of the infrastructure is now in place.
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APPENDIX B
Policy Matrix
The following matrix attempts to align the recommendations arising from the Final Report for the
Study on an Official Adoption of the NSCRS [Sept, 2003] with the policies the Province of Nova
Scotia is hereby implementing :
Policy
(Refer to Section 2.2 of this document)
Recommendation from the “Official
Adoption of the NSCRS”
(Refer to Section 5 of that document)
1.0 Administration of Policy
was not raised specifically by study
2.0 Operational Approach
1, 5, 8, 9
3.0 Consultation: Engaging Stakeholders
1, 2, 3
4.0 Communications: Opening Dialogue
1, 2, 3
5.0 Standards and Specifications
was not raised specifically by study
6.0 Geodetic Reference System
6
7.0 Monitoring Change
1, 7
8.0 Coordinate Transformation Services
8, 9
9.0 Nova Scotia Coordinate Control System (NSCCS)
10, 11
10.0 Vertical Reference System
was not raised specifically by study
11.0 Nova Scotia High Precision Network (NSHPN)
was not raised specifically by study
12.0 Error Ellipse Information
11
13.0 Metadata
was not raised specifically by study
14.0 Small Scale Map Projections
12
15.0 Large Scale Map Projections
13
16.0 Grid Shift Files
8, 9
Note: Not covered in this policy document
4, 14
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APPENDIX C
Terminology
Definitions / Acronyms
The following Appendix presents a standard set of definitions for NSCRS related policy material.
In cases where other source definitions differ, the definitions contained within will supercede others.
Communication is vitally important to managing the coordinate reference system. Since 1968 not
only has technology changed within the Nova Scotia coordinate reference system but so has the
terminology. In some instances it has been imperative that a term or concept be renamed/ newly
referenced so as to attempt to bring clarity of thought within the positioning community.
ATS77 (Average Terrestrial System 1977) - ATS77 is a geocentric coordinate system defined by
GSD in 1977 for the Maritime provinces. It is a conceptualization of a conventional terrestrial
reference system using the ATS77 reference ellipsoid. The ATS77 reference frame was realized by
a set of coordinates in the ATS77 system. The coordinates were obtained from the 1979 Maritime
Redefinition and Readjustment of the combined three provincial geodetic networks then in
existence. ATS77 is now known to be offset from the true geocenter by about 5 m.
Canadian Spatial Reference System (CSRS) - The collection of procedures, models, conventions,
standards, objects, observatories and related data, which are logically combined together and used
in Canada to establish and maintain the national reference frame. It provides for a quantitative
description of positions, motions, and gravity in space and time and, includes a description of the
physical environment. Through it, it is possible to determine from observations the coordinates of
the frame points that define the reference frame(s) and, to improve the adopted coordinate values
as new observational data and techniques are accumulated and/or implemented. It ensures continuity
of the national reference frame and its compatibility with international standards, as well as serving
as a “source” in the development and maintenance of a global spatial reference frame.
Collection Level Metadata - information related to an overall collection of products. (compare with
Product Level Metadata)
Control System - term that has historically been used, to describe a system of coordinates for
control points. Many positioning users have viewed this set of coordinates for control points as a
datum, as they are being held fixed and used as the reference for subsequent computations. This has
led to much confusion about the definition of the term “horizontal datum”. The “textbook” definition
is a reference surface; i.e., a reference ellipsoid appropriately positioned with respect to the Earth’s
surface. The control points and their set of coordinates would be equivalent to the modern concept
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of “reference frame”.
Coordinate frame – a set of rectangular axes (or other geometrical construction) with respect to
which the position of a point may be specified.
Frame Point - is one of the points from the set of physical points that serve to realize a reference
system. It is at these points where comprehensive and accurate observations are made that are then
used to determine the point’s position (coordinates) in accordance with the principles and
specifications of the reference system and thereby realize it - i.e. takes the reference system from
something conceptual in nature and makes it real, tangible and accessible.
Grid Shift File - a data file containing an estimate, at regularly spaced grid intervals across an area
of interest, of the coordinate shift between two sets of coordinates. It represents a model that can be
used for performing transformations between two reference frames.
Map Projection
(1)
is the orderly transfer (mapping) of the position of points or objects from the ellipsoidal
surface representing the earth to corresponding points on a flat surface, i.e. a map plane.
(2)
the mathematical mapping (transformation) that projects points or objects on the
reference ellipsoid representing the earth, to horizontal positions on a two dimensional
mapping surface such as a cylinder or cone that can be developed (ie. laid flat) into a
plane.
MTM (Modified Transverse Mercator) - a Transverse Mercator map projection system used
by Nova Scotia to transfer (map) NAD27 positions from the ellipsoid to a plane coordinate
system.
NAD27 (North American Datum 1927) - A non-geocentric coordinate system used for North
America (Canada, United States and Mexico). It is a conceptualization of a Geodetic reference
system using the Clarke 1866 reference ellipsoid as the best-fitting surface. Astronomic
observations were used to position and orient the ellipsoid at a single datum point in the central
U.S. (Meades Ranch). The origin of this system is offset by approximately 250 m from the
geocentre. The original realization of this system was obtained from an adjustment done between
1927 and 1932 using all geodetic networks then in existence. New points and networks were
added in subsequent years by holding fixed the coordinates of any existing control points. In
later years this led to unacceptable distortions in many areas and regional readjustments were
performed to obtain a more homogeneous set of coordinates. One of these readjustments was
performed for Nova Scotia in 1972 and is known as the 1972 Nova Scotia Readjustment. The
resulting coordinates are designated NAD27 for Nova Scotia. Today, such a set of coordinates
would be considered a regional reference frame.
NAD83 (North American Datum 1983) - A geocentric coordinate system introduced in 1986
for North America, Central America (i.e., from Greenland to Panama), the Caribbean Islands and
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Hawaii. It is a conceptualization of a conventional Terrestrial reference system using the GRS80
reference ellipsoid. The origin of this system is offset by approximately 2 m from the geocentre.
The first realization of the system was obtained from the July 1986 Continental Adjustment,
using conventional survey data, Transit satellite Doppler data and VLBI data spanning the
countries listed above. Subsequently, a regional adjustment was performed by GSD to integrate
the primary (Federal) and secondary (Provincial) horizontal networks of Eastern Canada. This
adjustment was completed in 1989 and is known as the Eastern Secondary Integration Helmert
Block Adjustment (SIHBA). Only the Federal horizontal network data was included from Nova
Scotia. This set of coordinates (realization) is designated NAD83(Original) for Nova Scotia,
however, it is not a realization that was used for any provincial networks.
NSCCS (Nova Scotia Coordinate Control System) - The network of Nova Scotia control
points and their coordinates initially referenced to the NAD27 coordinate system and
subsequently, in 1979 referenced to the ATS77 coordinate system. The actual number of control
points used in the two situations is different, as some points did not exist or are not included in
the respective adjustments. Overall there are approximately 23000 control points. Today, the two
sets of control points and coordinates are each considered a reference frame.
NSCRS (Nova Scotia Coordinate Reference System) - The collection of geodetic
components (past, present and future), related data, standards, guidelines, and geodetic software
used by Nova Scotia to define, establish and maintain the provincial reference frame and the
associated products and services that, when taken together provides for a quantitative description
of positions in Nova Scotia. The provincial reference frame is integrated with and is an extension
of the national reference frame. The provincial reference frame is actually comprised of the
following layers (network hierarchy) of control points:
- the Canadian Base Network (CBN) points in Nova Scotia
- the Maritime High Precision Network (MHPN) points in Nova Scotia
- the MHPN Nova Scotia densification points
NSHPN (Nova Scotia High Precision Network) - the unified three-dimensional network of
control points in Nova Scotia observed with high precision using GPS. The network has a
nominal point spacing of 25 km, and is connected to the Canadian Base Network (CBN) and the
Maritime High Precision network(MHPN). The term NSHPN is often used to refer collectively
not only to the network of Nova Scotia densification points of the MHPN, but also to include the
Nova Scotia points from the CBN and MHPN as well.
NSMTM (Nova Scotia 3E Modified Transverse Mercator) – a Transverse Mercator map
projection system used by Nova Scotia to transfer (map) ATS77 positions from the ellipsoid to a
plane coordinate system. The same map projection is also used with NAD83 for large scale
mapping applications.
Plane Coordinate System – a two-dimensional (plane) rectangular coordinate system based
upon a particular projection of the points from the reference ellipsoid onto the plane surface. The
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axes of the 2D coordinate frame are oriented such that the positive direction of one points toward
the north and the positive direction of the other, points toward the east.
Positioning - the act / task of determining the position of a feature or object.
Product Level Metadata - Information about individual maps/products contained within a
collection, or standing alone. (compare with Collection Level Metadata)
Reference Coordinate System - a coordinate system with a defined origin, orientation of the
axes, and scale.
Reference frame - a set of physical points with precisely determined coordinates in a specific
coordinate system that provides a realization of a terrestrial reference system. It serves to define,
or realize a particular coordinate frame. The reference frame provides the geometrically
consistent physical structure that is the foundation for positioning tasks and to which real world
features can be spatially referenced. The term reference frame is often used as if it were
synonymous with the coordinate frame that it defines.
UTM - Universal Transverse Mercator – a worldwide system of Transverse Mercator
cylindrical mapping projections. Each projection zone is 6° wide and the central scale factor is
0.9996, however, these parameters may be varied in some jurisdictions. The central meridians
are at longitudes 3°, 9°, etc, east and west of Greenwich. For the northern hemisphere a false
easting of 500,000m and a false northing of 0m is used. In Nova Scotia the projection is often
used for small scale mapping applications, and for projects requiring complete provincial
coverage on one mapping plane.
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Acronyms
Acronyms
ATS77
CBN
CDGPS
CGVD28
CSRS
GPS
GSD
HPN
MTM
NAD27
NAD83
NSCCS
NSCRS
NSGC
NSHPN
SNSMR
UTM
VLBI
WGS84
Definition
Average Terrestrial System of 1977
Canadian Base Network
Canada-wide Differential Global Positioning System
Canadian Geodetic Vertical Datum of 1928
Canadian Spatial Reference System
Global Positioning System
Geodetic Survey Division
High Precision Network
Modified Transverse Mercator
North American Datum of 1927
North American Datum of 1983
Nova Scotia Coordinate Control System
Nova Scotia Coordinate Reference System
Nova Scotia Geomatics Centre
Nova Scotia High Precision Network
Service Nova Scotia and Municipal Relations
Universal Transverse Mercator
Very Long Baseline Interferometry
World Geodetic System of 1984
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APPENDIX D
Reference Material
Government of Nova Scotia, Control Survey Task Group, Land Information Systems Advisory
Committee, NS Land Use Committee, (November 1995). “A Coordinate Referencing Policy for the
Province of Nova Scotia”
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Summary Report on the Existing Administrative Instruments Governing the Reference System
Standard and Map Projection used by Provincial Departments in Nova Scotia. As prepared by
Jacques Whitford and Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Results of the User Feedback Process For the Study on the Official Adoption of the Nova Scotia
Coordinate Referencing System. As prepared by Jacques Whitford and Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Summary Report on the Administrative Instruments and Process Used by Other Provinces and the
Federal Government in regards to Coordinate Referencing Systems and Map Projections. As
prepared by Jacques Whitford and Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Future Developments in Reference Systems for the Study on the Official Adoption of the Nova Scotia
Coordinate Referencing System. As prepared by Jacques Whitford and Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Summary Report of the Workshop conducted at Acadia University on June 23, 2003 for the Study
on the Official Adoption of the Nova Scotia Coordinate Referencing System. As prepared by Jacques
Whitford and Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003),
Summary Report of the "Primary" Provincial Geospatial Databases For Study on the Official
Adoption of the Nova Scotia Coordinate Referencing System. As prepared by Jacques Whitford and
Watermark Industries Inc.
Government of Nova Scotia, Service Nova Scotia and Municipal Relations (September 2003), Final
Report for the Study of the Official Adoption of the NSCRS. As prepared by Jacques Whitford and
Watermark Industries Inc.
A Guide to Coordinate Systems in Great Britian. Ordnance Survey (2002)
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Demystifying Reference Systems. D. Junkins, G. Garrard, (Geomatica vol 52, No 4, 1998)
National Geodetic Infrastructure Requirements Study. (Prepared by Bearing Point, for Natural
Resources Canada, 2004)
On the Correct Determination of Transformation Parameters of a Horizontal Geodetic Datum. P.
Vanicek, P. Novak, M Craymer, S. Pagiatakis; (Geomatica Vol. 56, No. 4, 2002)
Reference Frames in Astronomy and Geophysics. (Ed) J. Kovalevsky, I.I. Mueller, B. Kolaczek,
(1989 Dordrecht; Kluwer)
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